The majority of confectionery processes require a primary step that involves the dissolution of sugar with or without additives in water. The resulting blend is then heated in various pieces of apparatus such as open kettles at atmospheric pressure or in closed vessels under vacuum or in thin film evaporators with or without vacuum and with or without scraping vanes. One of the primary functions of the cooking process is to evaporate off enough water to produce the proper consistency in the final product. Cooking in open vessels is a slow tedious labor intensive process. Thin film evaporation is much faster but involves the use of very expensive equipment.
For example when a hard candy batch is made in an open kettle, the sugars are dissolved in approximately 20% water after which the solution is boiled until the water content is reduced to approximately 1%. During the boiling process an operator has to continually wash down syrup that splashes on the side of the vessel in order to prevent that portion from crystallizing which would reduce the clarity of the entire batch.
In production of hard candy with a thin film evaporator it is advisable to use stainless steel on the evaporating surfaces for sanitary reasons. The vessel has to be composed of sturdy walls because it is usually advisable to evaporate under vacuum to prevent excessive color formation. The walls must be rigid in order to maintain almost perfect smoothness on the evaporating surface and the proper clearance especially when vanes are used. A pump is used to deliver the syrup to the evaporator and another pump is used to remove the concentrated product. A condenser is also necessary in order to remove the resulting vapors from the evaporation process. As is evident these processes are expensive either due to the labor involved or to the sophistication of the equipment required in automated systems.